Journal of Machinery Manufacture and Reliability最新文献

In mechanical engineering, the processes of cast blank production compete with the processes of metal forming. This competition intensifies when comparing the properties of structural materials such as steel and aluminum-based alloys. Based on the results of research and a comparative analysis of various solutions, a technological scheme of horizontal plunger die-casting, free filling of the mold cavity with liquid metal, and the application of high pressure to the crystallizing metal is developed. The option of casting and applying pressure aimed at suppressing ring-shaped casting shrinkage is considered. The advantages and disadvantages are determined. The possibilities of expanding the scope of application are named. The requirements for the equipment design and for the control means, process regulation and control are determined.

The results of theoretical studies aimed at justification of the stress–strain state of the high-load friction units in a MMS-70×23 Gidrofol mill for raw-material self-grinding at the first grinding stage are presented; the mill has a volume of 80 m³ and plain bearings restored by gas-thermal spraying. The operation of the coated plain bearing–rotating trunnion system has been demonstrated. The main directions of theoretical studies have been formulated and the directions of further experimental studies have been justified.

The existing types of drives for hydraulic emergency rescue tools used to perform special work during fires and to eliminate the consequences of road accidents are considered. The main shortcomings of existing drives have been identified. A new drive design is proposed and described, in which compressed air from the cylinders of gas and smoke protection breathing apparatus is used as an energy source. A three-dimensional model of the designed drive is presented. The main technical parameters of the developed design and the results of tests of the prototype are presented.

The vibrations that arise in a system when several rotors with a small spread of dynamic characteristics are mounted on the elastic base are studied. Symmetrical frame structures with both linear and nonlinear elastic characteristics are considered as a base. It is shown that, in these systems, the interaction of different vibration modes occurs due to the low asymmetry, and unstable resonance modes with sharp jumps in vibration amplitudes occur at certain rotor rotation speeds. A system consisting of four rotors mounted on an elastic square shock-absorbing frame is analyzed. The conditions for the occurrence of unstable modes and the most dangerous rotor rotation speeds are found. The calculated and theoretical results are given. The mathematical apparatus of the theory of representation of symmetry groups is used for analytical studies of a symmetric system.

The patterns of destruction of an abrasive and the walls of the channel of a nozzle attachment of a waterjet machine during the movement of a multiphase flow modified by surfactants are revealed. The results of modeling the kinematic characteristics of the motion of abrasive particles in a multiphase flow with surfactants, as well as the results of modeling the contact interaction of the abrasive with the walls of the nozzle of a waterjet machine are presented. Conclusions are made about the influence of the geometry of the nozzle channel profile on the destruction of the abrasive and the surface of the jet-forming channel.

Data on the reaction of the human body to the heat impact of woven electric heaters are obtained. To estimate the reaction results, the data are processed considering the calculation of the difference between the temperatures obtained in the heater area with variable and constant heat transfer coefficients to the human body. The obtained results are compared with those of the peripheral microcirculation study using plethysmography and laser Doppler flowmetry. The comparison shows both the coinciding and the original nature of the results; therefore, the proposed approach can be used independently and be combined with other methods, which will allow us to obtain more information about the effect of heat on the microcirculation processes of blood. This article is useful for experts developing heating devices for humans and medicine, as well as for physiologists and medical workers.

Several energy parameters of molecular models of polytetrafluoroethylene and its composite F4K20 are calculated. As a result of friction and wear modeling, the energies of intermolecular bonds in the volume of the constructed (U_{{{text{inter}}}}^{{text{V}}}) models, in the surface zone (U_{{{text{inter}}}}^{{text{S}}}), and at the transfer layer–counterbody interface are determined, and the shear moduli of the material models under study are assessed. It is found that, in F4K20, compared with the original matrix, all of the above parameters increase, which may indicate stabilization of the kinetic state of molecules in the presence of a filler. Based on the results of a comparative analysis of (U_{{{text{inter}}}}^{{text{V}}}), (U_{{{text{inter}}}}^{{text{S}}}), and (U_{{{text{inter}}}}^{{{text{ad}}}}) with the value of the linear wear rate determined for the materials under study as a result of tribological tests, the (U_{{{text{inter}}}}^{{text{V}}}) value is proposed as a wear-sensitive criterion at the molecular level, and the (U_{{{text{inter}}}}^{{{text{ad}}}}) value is proposed as an additional parameter characterizing the adhesive strength of the transfer layers.

The bending and vibration characteristics have been investigated of the piston pin of internal combustion (IC) engine using where ANSYS 17.2 software. Piston pin is the main component of IC engine’s piston connecting rod assembly; which play a crucial role in transmitting gas force from piston to connecting rod to crankshaft. Design of piston pin needs the awareness of various boundary conditions, loading conditions and developed stress resultant (N_xx, N_yy, N_xy). It is also desires the information of materials, various types of surface treatments to increase its fatigue strength and avoid various modes of failures. Here, bending behavior of piston pin has been studied under mechanical and thermal load conditions after that analyzed the various stresses such as shear stress (τ_xz, τ_yz) and bending stress (σ_xx, σ_yy, σ_xy). Moreover, the empirical formulas for piston pin geometry, clearance, importance of piston pin offset, and complete design procedure of IC engine piston pin is expressed. In this communication the effect of various boundary conditions (fully floating piston pin, semi floating piston pin and stationary piston pin), loading conditions, material properties (Material 1–4), inner cross section of piston pin has been investigated.

A simplified method for calculating the secondary field in the far field of a finite cylindrical shell immersed in a liquid is proposed. A comparative assessment of the components of the total field associated with radiation caused by shell vibrations and sound reflection from an absolutely solid body is given. Recommendations for the use of the simplified method are given.

When designing thin-walled structures made of composite materials, the fundamental initial data are the unidirectional layer characteristics which depend to a large extent on the properties of the matrix and its adhesion to the fiber. In this paper, using the Rabotnov nonlinear constitutive relation, the regularities of deformation of a unidirectional carbon fiber-reinforced thermoplastic at high temperature under in-plane shear conditions are described. The application of the properties of resolvent operators used in hereditary mechanics of solids and the choice of approximation of the instantaneous stress–strain curve made it possible to invert the Rabotnov constitutive relation. Comparison with the experimental results showed the correctness of the proposed approach.